1. Field
The present disclosure generally relates to multi-chip modules (MCMs) and techniques for fabricating MCMs. More specifically, the present disclosure relates to an MCM that includes substrates with positive and negative features that mate and self-lock, thereby mechanically coupling the substrates.
2. Related Art
Wire bonding and solder-ball flip-chip bonding are widely used in electronic packages to produce first-level or chip-to-substrate interconnects. With the recent emergence of multi-chip modules (MCMs) which use large-area substrates, there is increasing interest in remateable interconnects between chips and a ceramic substrate to address the so-called ‘known-good-die issue.’ Additionally, chips are often fully tested prior to assembly of an MCM because it is expensive to replace the ceramic substrates in the MCM in the event of a bad or faulty chip. However, such rigorous testing prior to assembly increases the cost of the MCM.
Stressed-metal springs or claws (which are sometimes referred to as ‘micro-springs’) are promising candidates for use in remateable chip-to-package interconnects. In particular, micro-spring interconnects offer low-resistance electrical contacts even after multiple engage-disengage cycles. FIG. 1 presents a block diagram illustrating an existing micro-spring connector 100, which can be fabricated by etching a sacrificial layer on a substrate to release a stressed-metal film.
When a micro-spring is deformed (for example, when it is compressed), there is a natural tendency for the micro-spring to return to its original stress-free state. As a consequence, a locking mechanism is often used to keep micro-springs compressed and in good contact with contact pads in an MCM at a designed compression height and alignment. For example, as shown in FIG. 2A, which illustrates an existing MCM 200, a chip and a ceramic substrate are held in place using an adhesive. Alternatively or additionally, as shown in FIG. 2B, which illustrates an existing MCM 250, an external clamp may be used.
However, while these locking mechanisms are remateable, they are generally incompatible with high-volume manufacturing in the semiconductor industry. In particular, these locking mechanisms often involve manual: alignment, placement and clamping.
Hence, what is needed is an MCM and a fabrication technique without the above-described problems.